The words ``Take good care of the baby, Carl''--practically the only words in Day's books about the lovable rottweiler--trigger giggles of delight from readers of all ages. And though Carl's Christmas has much in common with its predecessor, Carl Goes Shopping , the new book has charms all its own. Carl is imbued with enough ``good will towards man'' to warm a whole town, and on Christmas Eve he and his infant charge venture forth to spread holiday cheer. Carl donates a basket of goodies to the needy (the baby contributes his hat), then lends his ``voice'' to a group of carolers. Back at home, awakened by strange sounds, Carl investigates; his expression as he comes face-to-face with his first reindeer is priceless. While this may not be Carl's most original adventure, it's still a delight, bound to please the good dog's old friends--and win him plenty of new ones. All ages. (Oct.)